Electric switch



Feb. 27, 1923.

1,446,828 G. A. BURNHAM ELECTRIC SWITCH 2 sheets-sheet 1 Filed July 10, 1919 Feb. 27, 1923.

G. A. BURNHAM ELECTRIC SWITCH Filed July 10,1919 2 sheets-sheet 2 Patented Feb. 27, 1923.

UNITED STATES PATENT OFFICE.

GEORGE A. BURNHAM. OF SAUGUS, MASSACHUSETTS, ASSIGNOR TO SEARS B. CONDIT, .13., OF BROOKLINE, MASSACHUSETTS.

ELECTRIC SWITCH.

Application filed July 10,

T all whom it may concem:

Be it known that I, Gnonon A. BURNHAM, a citizen of the United States, and resident of Saugus, in the county of Essex and State of Massachusetts, have invented an.Improvement in Electric Switches, of which the following is a specification.

M invention relates to electric switches and has more particular reference to an electric switch having a high current interrupting capacity.

he current interrupting capacity of an electric switch depends, among other things, upon the length of time during which the 16 are persists upon the opening of the switch. The shorter this period, the higher may be the current interrupting capacity of the switch because of the shorter time during which the arc may act upon the oil and, by its heat, vaporize it to thereby build up a gaseous pressure within the switch.

An object of my invention, therefore, is to provide means whereby the opening of the switch may be rapidly and quickly performed to thereby limit the duration of the arc to but a short period.

A further object of my invention is to provide means whereby the opening movement of the switch is automatically accelerated by the pressure developed within the switch caused by the interruption of the circuit controlled thereby.

The means whereby I accomplish these objects of my invention is by the provision of a member associated with the switch operating mechanism operable to rapidly move said mechanism into open position upon the development of a pressure within said switch.

More specifically, the means comprises a piston operable within a cylinder and communicating with the gas expansion chamber of the switch and connected through proper and preferably, speed-increasing, linkages with the movable switch member. Upon the control of the switch by external means to open it and due to the pressure which may be consequently set up therein, said piston is actuated by such pressure to accelerate the initial switch opening movement to thereby the more rapidly move the switch member into full open position thereby the more quickly to interrupt the circuit. By the provision of such means the interrupting ca- 1919. Serial No. 309,854.

pacity of a switch having certain physical dimensions may considerably increased.

Fig. 1 is a sectional elevation of anelectric switch embodying my invention.

Fig. 2 is a plan view of the switch illustrated in Fig. 1.

Fig. 3 is a detail of the switch operating mechanism showing the relative positions of the operating component in the open position of the switch.

Fig. 4: is a detail illustrating the application of my invention to a switch having a modified arrangement of switch operating mechanism.

As here shown, the switch with which my invention is associated includes the stationary switch members 10 secured in the switch frame 11 and the movable switch member including the brush member 12 supported on the end of the switch rod 13 passed through the bushing 14 of the switch frame 11.

The switch operating mechanism is of the type arranged to move the brush member 12 in an approximately straight line and comprises the links 15 pivotally secured to the yoke 16 from which the switch rod 13 is supported. Said links are pivoted at their other ends to the links 17 which are pivotally secured at their lower ends to the pin 18 secured in the switch frame. Guide links 19 are pivoted to said links 15 intermediate the ends'thereot and at their free ends are pivoted to the lugs 20 formed on the switch frame. A bell cranklever, comprising the single arm 21 and the dual spaced-apart arms 22, is pivoted on said pin or shaft 18 and said dual arms 22 are pivotally connected through the links 23 with said links 15.

The operation of said bell crank lever by external means serves to move said movable switch member into closed or open position and said movable switch member is adapted to be locked in closed posit-ion by the alignment of said arms 22 of said lever and links 23. A slight movement of said bell crank lever to break the toggle formed by said lever and said links 23 is sufiicient to permit the weight of the movable switch member and associated mechanism to operate to move said movable switch member into full open position.

The oil receptacle 25 is of more or less common construction and is removably se- :pivotally secured at its cured to the switch .trame by the bolts 26 and wing-nuts 27. Oil is adapted to be con tained in said receptacle in which the movable and stationary switch members are immersed and the space between the surface of the oil and the switch frame constitutes an expansion space for gas and vapor formed upon the operation of the switch.

In carrying out my invention for the automatic acceleration of the movable switch member into full open position, I provide cyl'1'noler30 which may be integral with the switch frameas shown or otherwise secured thereto and in communication with the expansion space within the switch. Said cylinder isopen ended asshownf A piston 31 1s slidably received within said cylinder and is. a more or, less tight fit therein. Said piston is adapted to be moved outwardly in its cylinder upon the building up of a pressure within the switch to accelerate the nrmvement of the switch member into open position. For this purpose a connecting rod 82 is pivotally secured to said piston 31 as by shall and socket connection and is upper end to the double-armed lever 34-. which is pivotally secured at 35 to the lugs 36- errtend'ed upwardly from the switch frame. The other end of said lever is pivotally connected at 3'? to links 38 which are in turn connected. at 39 to the switch operatinglevers 15.

Under normal conditions of switch operation in which but small pressure is developed within. the switch. it is seen that the piston. will be reciprocated within its cyliiider by the movement of the switch operating mechanism. without in itself acting in any appreciable'degree upon said mechanism.

Upon the beginning of the'interruption of a ctircuit having 'an abnormal value of current therein the arc formed between the movable and stationary switch members may cause an appreciable pressure to be set up within the switch. This pressure acts upon the piston 31 and causes it to be forced upward in its cylinder and consequently acting through the lever 3st upon the switch operating mechanism to rapidly move the movable switch member into fullopen position and thereby serving to quickly and rapidly interrupt the circuit. ihe greater the pressure set up within the switcln the greater will be the :Eorce acting upon the switch operating mechanism and the more quickly will the movable switch member be moved into open position and conse quently the higher will be the current interrupting capacity 015 the switch.

In the modification shown. in Fig". l the switch mechanism is entirely enclosed in the enclosing casing 40. The 'swit'clropen ating rod, 13 of the movable switch member is pivotally connected at 41 to a guide link 42 which is pivotally connected at 43 to eaeco the lint: and said link is pivoted at as to a suitable support.

link to is pivoted at t? to V I extends on the other i e switch operating rod and is pivoted at 48 to a suitable support on the switch. it. bell crank lever 4-9 pivoted at 50 tothc switch is connected to said operating link 47 throughthe lin; 5i. and said bell crank lever and link 51 form a toggleby which the movable switch member is operated and rest-r ed closed pos ion. The

other arm of said bell crank lever is pivotally connectcd with an operating rod n this modification. the s stem's-r the switch accelerating device is integrally formed with the casing" 40. @[Thei iston 'fiti is slidably received therein. and has a connecting rod 5? rigidly associated therewith and extended downwardly withiirsaid enclosingcasing; 4Q. Said rod, therein which is receive'din the slot 58 oi the lever 59 which is pivoted at 60 to alug dependingfrom said casing 40. Theother end oi said lever is pivotally connected to a link 61 which is connected 'at'62 to "steal ting; lever 46., p p p p The operation of this device is identical with the operation of that shown in Fig l.

Upon a'pressure developed within theswitch due to the opening of the switch,'said 56 is moved upwardly tothereby 1d 'aress the operating rod 13 and consequenti the more rapidly to move the movable sw't' member to open position thereby thein'ore quickly to interrupt the circuit It is obvious that many moo v my invention may be made 'with'ont departing from the spirit thereof.

1 claim 1. An electric switch comprising station ary and movable switch members, and means toincrcase the speed otbpenin'g movement of the movable switch member for relatively high values of current arranged to be with out material effec'ttor relatively low "use of current, said means comprisi'ng' a"casing adapted to contain'a fluid in which the switch members are immersed and substantial gas expansion space above ths fiuid,

and a piston associated with the 'movable switch member to move ittoward s hopen position and in communication vith the gas expansion space and srrsn eato be effectively actuated by abnormalfgaseous pressures within said space an'dbe ineffective with small jgaseous pressures within said space. A

2. An electric switch comprising statibhary and movable switch members, and means including expansionspace to i'hcrease the speed of openingi'movenient of the movable switch member for relatively high values or" current arranged to be without material effect for relatively low values of current.

3. An electric switch comprising the combination of an enclosing casing adapted to contain a fluid and a substantial gas expansion space above the fluid, stationary and movable switch members immersed in the fluid, switch-operating mechanism connected with the movable switch member, and a piston connected with said operating mechanism arranged in communication with said gas expansion space to be effectivelyinfluenced only by abnormal gaseous pressures therein.

4. An electric switch comprising the combination of an enclosing casing adapted to 

